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Letters to the Editor Insights into Digital Tomosynthesis of Interstitial Lung Disease From: Alexis Lacout, MD, Department of Radiology, Centre d’Imagerie Médicale, 47 boulevard du Pont Rouge, 15000 Aurillac, France Pierre-Yves Marcy, MD, Department of Medical Imaging, Polyclinique Les Fleurs, Ollioule, France e-mail: [email protected]
Editor: We read with great interest the article by Chou et al, “Digital Tomosynthesis of the Chest: Current and Emerging Applications” (1). The article provides a detailed and comprehensive review with excellent illustrations from chest examinations with digital tomosynthesis (DTS). We offer the following supportive comments based on our experience. Flat-panel DTS, by eliminating the visual clutter of overlying anatomy, has the potential to improve diagnostic performance beyond levels achievable with conventional radiography. Although it does not offer the contrast resolution of computed tomography (CT), DTS does allow high-spatial-resolution imaging of the lung anatomy in the plane of acquisition, at a dose and a cost that are expected to be lower than those for CT. In addition to the applications described by Chou et al, improved pulmonary fibrosis evaluation is possible with DTS, which allows excellent depiction of parenchymal lesions as small as 200 μm in the plane of acquisition; by comparison, CT permits detection of lesions that are 500 μm or more in diameter. Thus, DTS may more precisely disclose subtle and tiny pulmonary lesions, helping improve the differentiation of a honeycomblike nodular pattern from an intralobular reticulonodular pattern (Fig 1), a challenging task at CT (2). The resultant improvement in diagnosis of interstitial lung disease may allow differentiation between types of lung fibrosis for which prognosis and treatment are markedly different (eg, between idiopathic lung fibrosis with
predominant honeycombing and nonspecific interstitial pneumonia with predominant groundglass opacities) (3). In the future, we believe that further improvement in spatial resolution with DTS will help improve differentiation also between other types of ground-glass opacities, such as those characteristic of alveolar disease (Fig 2) and those related to fibrosis. Further studies are needed to precisely define the role of DTS in diagnostic workup and in follow-up evaluation of fibrotic lung diseases.
References 1. Chou SH, Kicska GA, Pipavath SN, Reddy GP. Digital tomosynthesis of the chest: current and emerging applications. RadioGraphics 2014;34(2): 359–372. 2. Lacout A, Thariat J, Fohlen A, Marcy PY. Tomosynthesis: a new chest imaging technique. Diagn Interv Imaging 2012;93(1):72–74. 3. Mink SN, Maycher B. Comparative manifestations and diagnostic accuracy of high-resolution computed tomography in usual interstitial pneumonia and nonspecific interstitial pneumonia. Curr Opin Pulm Med 2012;18(5):530–534.
Dr Chou and colleagues respond: We sincerely appreciate the interest of Drs Lacout and Marcy in our article and their insightful comments about the capacity of digital tomosynthesis (DTS) for the evaluation of interstitial lung disease. We agree that DTS provides high spatial resolution. As we mentioned in our article, “This flatpanel detector [in DTS] provides higher in-plane spatial resolution—most commonly a 200 × 200μm pixel size, compared with a pixel size of approximately 500 × 500 μm at CT” (1). We share a similar outlook regarding the prospects of DTS for the assessment of pulmonary parenchymal disease, specifically interstitial lung disease, which are appropriately illustrated by the figures in the letter above as well as by the review article by Drs Lacout and Marcy (2). This potential application of DTS is discussed in the section on “Cystic Fibrosis and Other Pulmonary Parenchymal Diseases” in our article (1). At the time when our article and this response were written, only a few reports of investigations of this specific use of DTS were available in the literature; these
Letters to the Editor should be submitted at http://ms.manuscriptcentral.com/rg.
LETTERS TO THE EDITOR
1871
1872 November-December 2014
radiographics.rsna.org
Figure 1. Pulmonary fibrosis in a 70-year-old man. A, an axial CT scan, shows tiny peripheral intralobular reticulations. B, a coronal image from DTS (left) with a magnified view of the region of interest (right), allows improved detection of reticulations, thanks to the high spatial resolution provided by the technique. Figure 2. Infectious pneumonia in the upper lobe of the left lung in a 39-yearold woman. Coronal image from DTS shows a focal region of consolidation (arrow) with an air bronchogram (arrowheads) and ground-glass opacity (*). In this setting, ground-glass opacity is secondary to alveolar disease; thus, the DTS image does not show either reticulation or honeycombing.
studies were focused on cystic fibrosis (3,4) and asbestosis (5). These articles suggested greater sensitivity and interobserver agreement with DTS than with radiography in detecting cystic fibrosis and asbestos-related changes (4,5); however, direct comparison between DTS and CT for detecting these disease processes has not been reported. We therefore hope to see future investigations that explore this application of DTS.
References 1. Chou SH, Kicska GA, Pipavath SN, Reddy GP. Digital tomosynthesis of the chest: current and emerging applications. RadioGraphics 2014;34(2): 359–372. 2. Lacout A, Thariat J, Fohlen A, Marcy PY. Tomosynthesis: a new chest imaging technique. Diagn Interv Imaging 2012;93(1):72–74. 3. Vult von Steyern K, Björkman-Burtscher I, Geijer M. Tomosynthesis in pulmonary cystic fibrosis with comparison to radiography and computed tomogra-
phy: a pictorial review. Insights Imaging 2012;3(1): 81–89. 4. Vult von Steyern K, Björkman-Burtscher IM, Höglund P, Bozovic G, Wiklund M, Geijer M. Description and validation of a scoring system for tomosynthesis in pulmonary cystic fibrosis. Eur Radiol 2012;22(12):2718–2728. 5. Lee G, Jeong YJ, Kim KI, et al. Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2013;68(4):376–382.
Shinn-Huey S. Chou, MD, Greg A. Kicska, MD, PhD, Sudhakar N. Pipavath, MD, Gautham P. Reddy, MD, Department of Radiology, University of Washington, 1959 NE Pacific St, UW Mailbox 357115, Seattle, WA 98195-7115 e-mail: [email protected]
Letters to the Editor Insights into Digital Tomosynthesis of Interstitial Lung Disease From: Alexis Lacout, MD, Department of Radiology, Centre d’Imagerie Médicale, 47 boulevard du Pont Rouge, 15000 Aurillac, France Pierre-Yves Marcy, MD, Department of Medical Imaging, Polyclinique Les Fleurs, Ollioule, France e-mail: [email protected]
Editor: We read with great interest the article by Chou et al, “Digital Tomosynthesis of the Chest: Current and Emerging Applications” (1). The article provides a detailed and comprehensive review with excellent illustrations from chest examinations with digital tomosynthesis (DTS). We offer the following supportive comments based on our experience. Flat-panel DTS, by eliminating the visual clutter of overlying anatomy, has the potential to improve diagnostic performance beyond levels achievable with conventional radiography. Although it does not offer the contrast resolution of computed tomography (CT), DTS does allow high-spatial-resolution imaging of the lung anatomy in the plane of acquisition, at a dose and a cost that are expected to be lower than those for CT. In addition to the applications described by Chou et al, improved pulmonary fibrosis evaluation is possible with DTS, which allows excellent depiction of parenchymal lesions as small as 200 μm in the plane of acquisition; by comparison, CT permits detection of lesions that are 500 μm or more in diameter. Thus, DTS may more precisely disclose subtle and tiny pulmonary lesions, helping improve the differentiation of a honeycomblike nodular pattern from an intralobular reticulonodular pattern (Fig 1), a challenging task at CT (2). The resultant improvement in diagnosis of interstitial lung disease may allow differentiation between types of lung fibrosis for which prognosis and treatment are markedly different (eg, between idiopathic lung fibrosis with
predominant honeycombing and nonspecific interstitial pneumonia with predominant groundglass opacities) (3). In the future, we believe that further improvement in spatial resolution with DTS will help improve differentiation also between other types of ground-glass opacities, such as those characteristic of alveolar disease (Fig 2) and those related to fibrosis. Further studies are needed to precisely define the role of DTS in diagnostic workup and in follow-up evaluation of fibrotic lung diseases.
References 1. Chou SH, Kicska GA, Pipavath SN, Reddy GP. Digital tomosynthesis of the chest: current and emerging applications. RadioGraphics 2014;34(2): 359–372. 2. Lacout A, Thariat J, Fohlen A, Marcy PY. Tomosynthesis: a new chest imaging technique. Diagn Interv Imaging 2012;93(1):72–74. 3. Mink SN, Maycher B. Comparative manifestations and diagnostic accuracy of high-resolution computed tomography in usual interstitial pneumonia and nonspecific interstitial pneumonia. Curr Opin Pulm Med 2012;18(5):530–534.
Dr Chou and colleagues respond: We sincerely appreciate the interest of Drs Lacout and Marcy in our article and their insightful comments about the capacity of digital tomosynthesis (DTS) for the evaluation of interstitial lung disease. We agree that DTS provides high spatial resolution. As we mentioned in our article, “This flatpanel detector [in DTS] provides higher in-plane spatial resolution—most commonly a 200 × 200μm pixel size, compared with a pixel size of approximately 500 × 500 μm at CT” (1). We share a similar outlook regarding the prospects of DTS for the assessment of pulmonary parenchymal disease, specifically interstitial lung disease, which are appropriately illustrated by the figures in the letter above as well as by the review article by Drs Lacout and Marcy (2). This potential application of DTS is discussed in the section on “Cystic Fibrosis and Other Pulmonary Parenchymal Diseases” in our article (1). At the time when our article and this response were written, only a few reports of investigations of this specific use of DTS were available in the literature; these
Letters to the Editor should be submitted at http://ms.manuscriptcentral.com/rg.
LETTERS TO THE EDITOR
1871
1872 November-December 2014
radiographics.rsna.org
Figure 1. Pulmonary fibrosis in a 70-year-old man. A, an axial CT scan, shows tiny peripheral intralobular reticulations. B, a coronal image from DTS (left) with a magnified view of the region of interest (right), allows improved detection of reticulations, thanks to the high spatial resolution provided by the technique. Figure 2. Infectious pneumonia in the upper lobe of the left lung in a 39-yearold woman. Coronal image from DTS shows a focal region of consolidation (arrow) with an air bronchogram (arrowheads) and ground-glass opacity (*). In this setting, ground-glass opacity is secondary to alveolar disease; thus, the DTS image does not show either reticulation or honeycombing.
studies were focused on cystic fibrosis (3,4) and asbestosis (5). These articles suggested greater sensitivity and interobserver agreement with DTS than with radiography in detecting cystic fibrosis and asbestos-related changes (4,5); however, direct comparison between DTS and CT for detecting these disease processes has not been reported. We therefore hope to see future investigations that explore this application of DTS.
References 1. Chou SH, Kicska GA, Pipavath SN, Reddy GP. Digital tomosynthesis of the chest: current and emerging applications. RadioGraphics 2014;34(2): 359–372. 2. Lacout A, Thariat J, Fohlen A, Marcy PY. Tomosynthesis: a new chest imaging technique. Diagn Interv Imaging 2012;93(1):72–74. 3. Vult von Steyern K, Björkman-Burtscher I, Geijer M. Tomosynthesis in pulmonary cystic fibrosis with comparison to radiography and computed tomogra-
phy: a pictorial review. Insights Imaging 2012;3(1): 81–89. 4. Vult von Steyern K, Björkman-Burtscher IM, Höglund P, Bozovic G, Wiklund M, Geijer M. Description and validation of a scoring system for tomosynthesis in pulmonary cystic fibrosis. Eur Radiol 2012;22(12):2718–2728. 5. Lee G, Jeong YJ, Kim KI, et al. Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2013;68(4):376–382.
Shinn-Huey S. Chou, MD, Greg A. Kicska, MD, PhD, Sudhakar N. Pipavath, MD, Gautham P. Reddy, MD, Department of Radiology, University of Washington, 1959 NE Pacific St, UW Mailbox 357115, Seattle, WA 98195-7115 e-mail: [email protected]
